Measurement of atomic hydrogen density in the plasma boundary region of inductively coupled plasma by VUV absorption spectroscopy

Plasma parameters can be analyzed by applying a VUV absorption spectroscopic method to the plasma through VUV light generated by He/H2 discharge. The VUV light source can provide a variable for measuring the atomic density of hydrogen based on the absorption spectroscopy. The VUV light source based on a hollow cathode discharge was used for an intense emission of 121.56 nm (Lyman-$\alpha )$ line. For accurate measurement of the hydrogen density, the self-absorption-applied vacuum ultraviolet absorption spectroscopy (VUVAS) was employed to Ar/H2 inductively coupled plasmas (ICP). The absolute density of hydrogen atoms was investigated for various Ar/H2 gas ratio in the ICP. In this way, the absorption of the hydrogen is about 35 {\%} at 50 mTorr and 100 W in inductively coupled plasmas (ICP). The hydrogen density was varied from 10$^{\mathrm{13}}$ §¯$^{\mathrm{-3}}$ to 10$^{\mathrm{14}}$ §¯$^{\mathrm{-3}}$ with respect to gas ratios with regard to absorption.